This invention relates to a fully automatic working vehicle comprising a time setting means, and automatic travel devices. This vehicle can move from its garage to the operation site, automatically controlling its course of travel (detouring obstacles and restricted areas) and operation, and return automatically to the garage. No personal supervision is required. Its typical embodiment is a fully automatic lawn mower.
The lawn mower has gradually developed --back-carried, hand-pushed, self-propelled, riding--and the burden to the operator has been considerably reduced. However the route of each lawn mower had to be controlled by a person. Further, a remote control type mower, like U.S. Pat. No. 4,545,453 requires an operator. Therefore, a lawn mower which can be operated automatically, without manpower or personal supervision, has become the final object of such development.
U.S. Pat. Nos. 3,425,197 and 4,133,404 disclose a lawn mower mounted with a device for detecting a margin position between the mowed area and the unmowed area to automatically guide the mower in circles (outside in or inside out) until the lawn is mowed within an area. However, its operation must be controlled by a person in the initial mowing circle, thus requiring some manpower. In U.S. Pat. No. 4,133,404, a mower comprises a function for detouring obstacles on the lawn, but the external area around the obstacle should be mowed in advance.
By means of memory and reproduction devices to produce signals for controlling the route, U.S. Pat. No. 3,840,086 discloses the use of recording tapes for route record and control. Republic of China Patent Application No. 7410043 employs a pen mounted upon a paper reel device for making a route record which then is read by a photoelectric cell in order for a servo-control to reproduce the route. However, such methods are based on preset procedures to control the machine's course of travel. Therefore, circumstances such as an incorrect starting position or direction, wheel slippage during travel, or touching an obstacle, will cause a deviation from the preset route and potential injury. Thus, the routing method with an open-loop control is deemed impractical.
The machine according to U.S. Pat. No. 4,180,964 comprises a metal wire (band) laid in a desired path as a conductor for controlling the pendulous position of a magnet on the lawn mower. Using electrical contact points and relevant mechanisms to correct its direction, the lawn mower moves along the wire. This technique is well-known and used in automation plants. Current in the wire generates an alternating magnetic field which induces the coils on the automatic vehicle to control the vehicle's movement. However, if this control method is used to control an entire lawn mowing route, a wire must be laid along the entire lawn mowing route, and obviously, it also is not practical.
Closed-loop control devices like directional detecting devices (such as a gyrocompass, infra-red, and/or ultrasonic waves) for detecting relative direction and distance in reference to points, or a vision device for multisensing are still at the laboratory stage because installation is complicated, reliability is unsatisfactory, and costs are high. Therefore, a low cost and reliable route control method is pending for presentation.
The achievement of the above-mentioned route control is only a part of the requirement of an automatic vehicle; in fact, a fully automatic vehicle must start automatically at a preset time, leave its parking place (e.g., a garage) for a starting position at the job site, and begin working. According to conditions at the job site, the fully automatic vehicle can perform various control functions, such as change speed, detour still obstacles, or restricted areas, and stop and warn objects moving through its path. Upon completion, or encountering an exceptional condition (insufficiency of fuel, rain, the job site being too wet), it will stop work automatically and return to the original parking place. In addition, the fully automatic vehicle has a burglar-proof function so that it can operate without any supervision at the job site.